Bonded webs, such as nonwoven fabrics are well known materials with wide application fields. Important applications encompass hygiene products and disposable articles, such as, for example, diapers. Many of these articles do not consist of a bonded web only, but include an elastomeric component to provide, for example, improved fit. This elastomeric component for instance is an elastic film. In a lamination process, the bonded web material is attached to this elastic film on one or on both sides of the film and provides the elastomeric component with a textile-like touch. Soft bonded webs are particularly suitable for such applications.
These laminates are generally produced on high-speed converting lines which apply tension in machine direction to the bonded webs. Applying tension to the bonded webs in machine direction will generally cause them to neck in, i.e. that their width is decreased. For obtaining optimal production, the bonded web is to completely cover the elastic film. However, during production, the tension applied to the bonded web varies. In such cases an ideal bonded web has a high dimensional stability, i.e. propensity to avoid neck-in in the cross-direction when under strain in the machine direction.
It is well known that a high dimensional stability can be obtained with bonded webs of high basis weight: the higher the basis weight of a bonded web, the higher is the force necessary to bring about neck-in. However, driven by the efforts to save raw materials and costs, low basis weights are desired instead of high basis weights. Thus, increasing the basis weight is prohibitive and other solutions that bring together low basis weights with high dimensional stability (under tension) are desired.
The technical challenge thus consists in bringing together and well balancing two contradicting properties: a sufficiently high cross-directional extensibility to allow mechanical activation, and a sufficiently high dimensional stability (low neck-in under machine direction tension) to make these materials processable on high speed converting lines.